Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations establish readOnly=false, destructive=false, idempotent=true; the description adds meaningful behavioral details beyond that: renderParams deep-merge semantics, scope-change re-baselining, and null values disabling channels. This goes beyond what annotations provide.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Three compact sentences; the first sentence front-loads the tool's purpose and key actions, the second clarifies update semantics, the third covers re-baselining and return value. No redundant content.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For an 11-parameter tool with nested objects, the description covers the essential behavioral contract: partial update, merge behavior, re-baselining, and return type. It doesn't enumerate every parameter, but the schema already does; the description adds the higher-level logic needed to use the tool correctly.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The schema already documents all 11 parameters with 100% coverage. The description adds cross-cutting semantic context that the schema cannot: partial-update behavior ('Only the fields you send change'), deep-merge for renderParams, and the re-baseline trigger for scope-related params. This is a slight but real lift above the schema baseline.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description opens with a specific verb ('Update') and resource ('a watch'), enumerating concrete update actions (pause/resume, re-point, change settings, turn off channels). This clearly distinguishes it from sibling tools like watch_create and watch_delete.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description establishes it as the in-place modification tool for existing watches, with explicit semantics for partial updates ('Only the fields you send change'). It does not explicitly name alternative tools, but the 'in place' framing and update verb make the usage context unambiguous.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.